Exhaust design help

[DP Racing]

depends on the motor and the application i guess. most of the information we recieved came from the engine builder as far as length, diameter and stepped or not on the primaries. what ive seen on the length v.s. size is usually a compromise between space and power range.

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[socalmoto]

Consider running a step header design. Run like 16" of 1.625 and then 16" of 1.75 into a merge collector.

i'd shoot for 26"-28" primaries.

Unfortunately the max length I can get is 18" or it becomes a problem getting it in where I want it.

Hmm, My cheesy exhaust calculator says for peak power at 5500RPM you need a 17.5" primary length.

Is this calculator on the internet or is it a program on your comp? Either way if you trust the cheesy calc its right in the length that I can make the headers so thats awesome how it worked out.

DO NOT weld as you go. make sure to only tack the primaries to the flange until they are completely built and welded (i learned the hard way). you will get the scavageing affect with only three primaries in the collector. before you put the collector on make sure to completely weld the area that will be inside the collector and laterally down the primaries 1"-2" where they are the closest, helps eliminate leakage. hope this helps.

I was going to tack everything till it was finished, but thanks for the tips on keeping it from leaking.

[partybarge_pilot]

Is this calculator on the internet or is it a program on your comp? Either way if you trust the cheesy calc its right in the length that I can make the headers so thats awesome how it worked out.

It's on My computer. I have checked it against some know headers I have and it always comes out really close. I'm about a week away from actually building a set off them. The longer they are the lower their peak will be. The 26-28" length posted above would put the peak about 4750, right in the middle of your target RPM range. I would shoot a little higher than that to prevent it from falling off the power band to quick.

[socalmoto]

It's on My computer. I have checked it against some know headers I have and it always comes out really close. I'm about a week away from actually building a set off them. The longer they are the lower their peak will be. The 26-28" length posted above would put the peak about 4750, right in the middle of your target RPM range. I would shoot a little higher than that to prevent it from falling off the power band to quick.

Sweet! I should be starting to build these around new years so well see how it goes.

[socalmoto]

Well I finally started on the headers today. I got the pasenger side almost done but had to rework the design for the driver side to clear the starter. 5 tubes are within 1% of the 17.75 length and one tube is 2% shorter.





Driver side. gonna start laying out the tubes tomorrow and hopefully start on the collectors

[Wahl_7s]

In my experience with a cross over on our 4.0 ford they are more trouble than they are worth! there is no noticeable difference from the seat of your pants. plus it makes the trans unserviceable in race situations without removing the exhaust. the truck runs like a 2 stroke the power begins at 3500 to the limiter (sorry i cant say what that is) my$.02.by the way nice job on the headers

[socalmoto]

In my experience with a cross over on our 4.0 ford they are more trouble than they are worth! there is no noticeable difference from the seat of your pants. plus it makes the trans unserviceable in race situations without removing the exhaust. the truck runs like a 2 stroke the power begins at 3500 to the limiter (sorry i cant say what that is) my$.02.by the way nice job on the headers

Thats awesome to know. I was planning on running true dual, but everyone keeps asking me if thats the best way . . . now I can say go on rdc and check for yourself hahah I kinda want that 2 stroke feeling too. If the power starts at 3500 that would be great . . . though our engine only hits 5500-6000 . . . not 12000 like yours probably does.


And heres the driver side headers. I still need to rework the lowest tube cause its too close to the starter, but no matter what we are way close to the starter and upper heim joint. A buddy is gonna give me some header wrap and Im gonna wrap the crap out of it . . . maybe itll save the starter